Direct copper electrodeposition on a chemical vapor-deposited ruthenium seed layer for through-silicon vias

Direct plating of Cu on Ru for dual damascene and high aspect ratio through-silicon via (TSV) structures requires high nucleation density and rapid coalescence of the Cu nuclei, which may be achieved by incorporating strong suppressors in the plating solution. Atotech Spherolyte plating chemistry, containing a unique strong suppressor, is able to generate a nucleation density greater than 10¹² cm^-2. No pretreatment of the Ru surface is necessary. Void-free, bottom-up fill has been repeatedly demonstrated within 40 min using this chemistry for 5 μm × 50 μm TSV structures without Cu seeds. Material characterizations including time-of-flight secondary ion mass spectrometry (ToF-SIMS) and electron backscatter diffraction (EBSD) analyses of the plated TSVs have been conducted and discussed.